linux-kernel - RE: [PATCH reset-next 2/2] reset: brcmstb: Fix 32-bit build with 64-bit resource_size

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Date:   Wed, 23 Jan 2019 14:23:24 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Florian Fainelli' <f.fainelli@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Brian Norris <computersforpeace@...il.com>,
        Gregory Fong <gregory.0xf0@...il.com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
        "sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
        "paul.gortmaker@...driver.com" <paul.gortmaker@...driver.com>
Subject: RE: [PATCH reset-next 2/2] reset: brcmstb: Fix 32-bit build with
 64-bit resource_size_t

From: Florian Fainelli
> Sent: 23 January 2019 00:34
> 
> On 32-bit architectures defining resource_size_t as 64-bit (because of
> PAE), we can run into a linker failure because of the modulo and the
> division against resource_size(), replace the two problematic operations
> with an alignment check on the register resource (instead of modulo),
> and the division with DIV_ROUND_CLOSEST_ULL().
> 
> Reported-by: Randy Dunlap <rdunlap@...radead.org>
> Fixes: c196cdc7659d ("reset: Add Broadcom STB SW_INIT reset controller driver")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  drivers/reset/reset-brcmstb.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/reset/reset-brcmstb.c b/drivers/reset/reset-brcmstb.c
> index 01ab1f71518b..c4cab8b5052d 100644
> --- a/drivers/reset/reset-brcmstb.c
> +++ b/drivers/reset/reset-brcmstb.c
> @@ -91,7 +91,8 @@ static int brcmstb_reset_probe(struct platform_device *pdev)
>  		return -ENOMEM;
> 
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> -	if (resource_size(res) % SW_INIT_BANK_SIZE) {
> +	if (!IS_ALIGNED(res->start, SW_INIT_BANK_SIZE) ||
> +	    !IS_AGLINED(resource_size(res), SW_INIT_BANK_SIZE)) {
>  		dev_err(kdev, "incorrect register range\n");
>  		return -EINVAL;
>  	}
> @@ -103,7 +104,8 @@ static int brcmstb_reset_probe(struct platform_device *pdev)
>  	dev_set_drvdata(kdev, priv);
> 
>  	priv->rcdev.owner = THIS_MODULE;
> -	priv->rcdev.nr_resets = (resource_size(res) / SW_INIT_BANK_SIZE) * 32;
> +	priv->rcdev.nr_resets = DIV_ROUND_CLOSEST_ULL(resource_size(res),
> +						      SW_INIT_BANK_SIZE) * 32;
>  	priv->rcdev.ops = &brcmstb_reset_ops;
>  	priv->rcdev.of_node = kdev->of_node;
>  	/* Use defaults: 1 cell and simple xlate function */

Isn't it enough to assign resource_size(res) to an 'unsigned int' ?
The value is never actually going to be over 4G.

	David

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